115/230 to 240v 3 phase?

[electricguy61]

Is there a transformer that will take standard residential voltage 120v/230v primary and convert it to 120v/208 3 phase secondary?

I find the the opposite (120v/208 3phase primary to 120/230v secondary, but is it safe to reverse the primary/secondary?

I have a customer that purchased a 3 phase piece of equipment and wants to run it at home.

Thanks

 

[infinity]

So you want to go from 3Ø, 240/120 to 3Ø, 208Y/120? Where are you getting 3Ø in a residence?

 

[electricguy61]

So you want to go from 3Ø, 240/120 to 3Ø, 208Y/120? Where are you getting 3Ø in a residence?

No, the customer wants to run a 3 phase piece of equipment at a residence that's has a single phase service

 

[templdl]

Is there a transformer that will take standard residential voltage 120v/230v primary and convert it to 120v/208 3 phase secondary?

I find the the opposite (120v/208 3phase primary to 120/230v secondary, but is it safe to reverse the primary/secondary?

I have a customer that purchased a 3 phase piece of equipment and wants to run it at home.

Thanks

Transformers are not able to change 1 phase to 3 phase. You must use a static or a rotary convertor in order to do so. Even though it my be a bit strange transformers can be designed to change 3 phase to1 phase.

 

[electricguy61]

Transformers are not able to change 1 phase to 3 phase. You must use a static or a rotary convertor in order to do so. Even though it my be a bit strange transformers can be designed to change 3 phase to1 phase.

That was my understanding. I've wired a couple of rotary convertors before.

Is static the one that uses only capacitors to basically simulate a phase?

 

[templdl]

F

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That was my understanding. I've wired a couple of rotary convertors before.

Is static the one that uses only capacitors to basically simulate a phase?

It is sort of like an AC varible frequence drive bhut the output is strictly 3ph60hz taking the 1ph source changing it to DC and then generation the 3ph output as it was explained to me I don't think that a phase could be slid 120deg with capacitors.

 

[mbrooke]

My advice would be to advise the customer change the motor out or find another machine that does the same job. Many times these are Ebay finds, which while look great cost wise, often are because they have limitations.


But, If the equipment must be used by the customer with no other option you could proably get away with one of these:

https://www.google.com/?gws_rd=ssl#q=ronk+add+a+phase

http://www.ebay.com/itm/like/181597933379?lpid=82&chn=ps&ul_noapp=true

Anything else will cost even more, and to be frank it supports my original stance: replacing the motor will be cheaper.

 

[kwired]

It is sort of like an AC varible frequence drive bhut the output is strictly 3ph60hz taking the 1ph source changing it to DC and then generation the 3ph output as it was explained to me I don't think that a phase could be slid 120deg with capacitors.

Neither static or rotary phase converters will output a perfect 120 degree phase differential between all three output leads. You generally will not want to run any motor at full load off one of these converters either because they will draw heavy current between two lines (usually the two that are same potential as the main input) and a lighter current on the others. Static converters are the worst unless you have a relatively fixed load, you need to fine tune how much capacitors are connected to get best possible loading balance, but change the load and you are either over or under what would be optimal.

A variable freq drive will be best for motors that will run at or near full load, or even need to vary in load. They will take a single phase input rectify it into DC then invert it back to three phase AC like you mentioned. Unless specifically designed for single phase only input, you do need to derate them when using single phase only as input.

 

[kwired]

If the machine or appliance your customer has isn't easy to convert to a single phase motor, or the machine is pretty expensive and worth the conversion equipment your best bet is to tell them to sell it and find a single phase version of the same machine.

Some instances you will spend about as much or more on conversion equipment then either changing the motor to single phase or even finding a different single phase machine. Sometimes three phase machines will sell cheap at auctions - because those interested in them do know it will cost them to get three phase to it so they won't buy it unless nobody is interested and then they get it cheap.

If it isn't a motor (say something with heating elements connected in delta configuration - you can just parallel them and still get full kVA capacity out of them - keep in mind you will still be same kVA but will be 1.732 times more amps then the nameplate says.

 

[ActionDave]

I agree with others, if it's just the one motor that's three phase change the motor and if you get a phase converter use a roto phase.

 

[Dzboyce]

I do it every day. It's called a vfd. 240 single phase in/240 3 phase out.

 

[Tony S]

A VSD would be the best option or you could use the Steinmetz system using a pilot motor

 

[Carultch]

Even though it my be a bit strange transformers can be designed to change 3 phase to1 phase.

I take it those transformers cannot be backfed? Standard transformers are usually bi-directional by default design.

 

[electricguy61]

On further investigation, (the customers first language is not English, so details were very hard to come by) I found the equipment had a 25 hp motor. The residence has a 100 amp service. Not gonna happen no matter what converter he tries :happysad:

 

[GoldDigger]

I take it those transformers cannot be backfed? Standard transformers are usually bi-directional by default design.

The Leyton transformer configuration can convert a three phase source to single phase, in such a way that all three of the original phases are equally loaded.
But if you try to drive it in the other direction there is no "information" available in the circuit to regenerate the three original phases.

Each transformer can be bi-directional, but the network formed by multiple transformers is not.

One way to look at the problem is that if you take two voltage sources in series the sum is uniquely determined. No problem.
But if you feed the series circuit from the outside there are an infinite number of voltage pairs that sum to that voltage.

If you drive the Leyton circuit with single phase and you also connect one of the three phase "inputs" to a solid source which has the correct voltage and phasing it will generate the other two phases. That is the best you can hope for.

 

[kwired]

On further investigation, (the customers first language is not English, so details were very hard to come by) I found the equipment had a 25 hp motor. The residence has a 100 amp service. Not gonna happen no matter what converter he tries :happysad:

It might work - you won't likely be running anything at the same time as the 25 HP motor though if you want the main OCPD to hold.